This invention relates to a pumping apparatus for use with automobiles as well as for industrial uses in general and for the feeding of a small amount of fuel under high pressure, and in particular to a pumping apparatus which employs the construction of a regenerative pump and/or a side channel pump in its part for the pumping action.
For example, general attention has been recently given to regenerative pumps as fuel pumps for automobiles.
However, conventional regenerative pumps are of the type for the feeding of a middle amount of fuel under high pressure and have characteristics such that the flow rate of fuel is largely varied with a change in discharge pressure. Accordingly, such regenerative pumps are not suitable as high pressure fuel pumps for vehicles which are required for feeding a small amount of fuel under high pressure and in which the flow rate of fuel is relatively slightly varied with a change in discharge pressures. In order that an one-stage type regenerative pump meets the requirements for high pressure fuel pumps, necessary measures will be taken in which sizes of flow channels representing a dimensional relationship between a pumping chamber and an impeller of this type of regenerative pump are made small or clearances defined between the impeller and the walls of the pumping chamber are made small or sizes of flow channels are made small and grooves formed in the impeller are small. However, any one of these measures is not suitable because pumping efficiencies are lowered or manufacturing costs are increased or pumping efficiencies are lowered and rotational speeds are increased to thereby increase a load on a driving motor.
Thus, with the arrangement of a prior regenerative pump, the external size thereof must be large or lateral clearances between an impeller and walls of a pumping chamber must be extremely small in order to raise discharge pressures, so that the pump occupies a large space and is difficult to manufacture.
Accordingly, there has been called for a pumping apparatus for the feeding of a small amount of fluid under high pressure which apparatus is smallsized and can discharge fluid of adequate pressure without the need of so high dimensional accuracy for the lateral clearances.